I am refering to the rpm where a machine's resonance frequencies will cause vibration to the point of self destruction. Within all industry it is important to run up a machine through its critical speed as quickly as possible, whether it be a pump, compressor, turbine or other mechanical device.

Due to adverse road conditions the other day I spent a lot of time around 3500 - 4000rpm at some point between these rpm the vibration was excessive and after a 200 mile ride I found various bolts had worked themselves loose, one side stand bolt fully fell out, the other was half way out and various other bolts had loosened.
A lot of work & time offshore is spent on condition monitoring and vibration analysis to prevent this on all rotating equipment, I am just wondering if anyone has noticed higher vibration at specific revs

some are aware of critical speeds, others are not, ideally when a critical speed is established it should be avoided.

I've never heard of a "critical speed" used in that context. Nor have I gone on a long cruise and found stuff falling off of my bike. Are you sure you aren't talking to the Harley owners? Maybe Carl can enlighten us as to what RPM a Harley starts to fall apart.

Beyond that, RPM wise, vibration issues would be the result of a poorly balanced engine.

F4 has it right, critical speeds exist where harmonics and tolerances combine to exponentially increase vibrations. Big commercial turbines have at least three critical speeds though which you pass quickly during turbine roll and start up to synchronous speed.

I'd say that you have discovered the "critical speed" for your F4...3500-4000 rpm.

It will be close to others, but it will be machine specific.

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Never get into an argument with a fool in an office cubical; passers-by won't know who's who. CRJ

I am refering to the rpm where a machine's resonance frequencies will cause vibration to the point of self destruction. Within all industry it is important to run up a machine through its critical speed as quickly as possible, whether it be a pump, compressor, turbine or other mechanical device.

Due to adverse road conditions the other day I spent a lot of time around 3500 - 4000rpm at some point between these rpm the vibration was excessive and after a 200 mile ride I found various bolts had worked themselves loose, one side stand bolt fully fell out, the other was half way out and various other bolts had loosened.
A lot of work & time offshore is spent on condition monitoring and vibration analysis to prevent this on all rotating equipment, I am just wondering if anyone has noticed higher vibration at specific revs

some are aware of critical speeds, others are not, ideally when a critical speed is established it should be avoided.

I've owned and rode a 1000s for years Roy and never had any of that happen to mine.

I've never heard of a "critical speed" used in that context. Nor have I gone on a long cruise and found stuff falling off of my bike. Are you sure you aren't talking to the Harley owners? Maybe Carl can enlighten us as to what RPM a Harley starts to fall apart.

Beyond that, RPM wise, vibration issues would be the result of a poorly balanced engine.

I've owned and rode a 1000s for years Roy and never had any of that happen to mine.

ade, I also have been riding F4's for 9 years but I have never sat between 3500 / 4000rpm for a considerable duration of time such as I did last week, normally on the EV03 I prefered to sit around 7000 - 8000rpm+, on the 312R and the 1000s I also prefer high up in the rev band, but as I previously mentioned due to appauling road conditions I was stuck at the lower mentioned revs for some considerable time, this is where I believe I have found the problem on my machine and the only explanation I can give is critical speed as its a thing I have dealt with often in the past whilst working with vibration analysis.
Riding through a critical speed is not a problem and should be encouraged, but to sit on a rpm similar to natural frequency is a problem.

Critical speed is a phenomenon, the same as compressor surge is, but both have wrecked machines time and time again.

This will be a one off for me, as I am aware of it now, up to yourselves if you want to take note on this or not.